Resolve "Automate API-tests"

Closes #62, #52, #51, and #23

See merge request cogsys/dare2del/demonstrator!22

Create dummy jobs only for MR into other branches.

System Tests

See merge request cogsys/dare2del/demonstrator!26

adapted new schema filenames

Closes #62

The previous definition could result in unexpected errors.
The previous oneof(...) throws an instantiation error
when the parsed term is not ground. This may happen for example
when a JSON object is parsed to a dict (tag is a variable).
The replacement has the same semantical meaning but avoids
throwing an instantiation exception when applied on a dict.

This reverts commit f2bc75f5.

Restrict /bg/clear to POST requests

Closes #60

See merge request cogsys/dare2del/demonstrator!25

for endpoints expecting none

for endpoints expecting payload